Report from the WG-2 of the LUMI-05 workshop scenarios for the injector complex upgrade

The LUMI-05 workshop was held in Arcidosso (Italy) from August 31st to September 3rd, gathering about 40 participants. The scope of the workshop was to explore scenarios for the LHC luminosity upgrade, with particular emphasis on LHC IR layouts with lower β* and on new high energy injectors for increasing the beam intensity. These topics were discussed by two separate working groups, the first one (WG-1) mainly dealing with the LHC IR Upgrade, and the second one (WG-2) on High Energy Injectors. This note reports about activities and conclusions of WG-2

LHC Luminosity and Energy Upgrade

LHC upgrade studies are ongoing as part of the EU CARE-HHH and of the US-LARP programmes. The aim is a ten-fold increase of the LHC luminosity by the middle of next decade, a possible upgrade of the injector complex to inject at 1 TeV and, at a later stage, to raise the collider energy. The motivations for the LHC upgrade are discussed. An overview of beam dynamics and technological challenges is presented. Preferred scenarios to maximize the integrated luminosity and the physics reach are identified

Possible scenarios for the LHC injector upgrade

The possible upgrade of the LHC injector chain is a crucial step towards the LHC luminosity upgrade beyond 1034 cm-2s-1. It is also a mandatory requirement for the LHC energy upgrade well beyond the ultimate value of 7.56 TeV per beam. By pushing the accelerator parameters to the ultimate performance we can increase to 1.7×1011 the bunch population and eventually reach a peak luminosity of 2.3×1034 cm-2s-1. To go beyond, a considerable improvement of the LHC parameters, such as ß*, beam intensity, bunch length, number of circulating bunches is required. Finally, the upgrade of the injector complex and of the injection energy is another important ingredient to upgrade both peak and integrated luminosity up to an order of magnitude above the nominal value

Scenarios for the LHC Upgrade

The projected lifetime of the LHC low-beta quadrupoles, the evolution of the statistical error halving time, and the physics potential all call for an LHC luminosity upgrade by the middle of the coming decade. In the framework of the CARE-HHH network three principal scenarios have been developed for increasing the LHC peak luminosity by more than a factor of 10, to values above 1035 cm−2s−1. All scenarios imply a rebuilding of the high-luminosity interaction regions (IRs) in combination with a consistent change of beam parameters. However, their respective features, bunch structures, IR layouts, merits and challenges, and luminosity variation with β∗ differ substantially. In all scenarios luminosity leveling during a store would be advantageous for the physics experiments. An injector upgrade must complement the upgrade measures in the LHC proper in order to provide the beam intensity and brightness needed as well as to reduce the LHC turnaround time for higher integrated luminosity

Injector upgrade: Dicussion and synthesis

We summarize the discussion on merits and drawbacks of various options for the injector upgrade, brought up at the second-to-last day of the LUMI06 workshop, notably the comparison of a normal-conducting and superconducting PS successor (PS2 and PS2+), items related to the SPS, and aspects of space-charge compensation

CARE-HHH-APD Workshop on Interaction Regions for the LHC Upgrade, DAFNE, and SuperB

This report contains the Proceedings of the CARE-HHH-APD Mini-Workshop “IR’07,” which was held in Frascati, Italy, from 7 to 9 November 2007. The central theme of the IR’07 Mini-Workshop was the upgrade of the LHC interaction region (IR). A second topic was the experience with the upgraded DAFNE IR as well as the ongoing plans and studies for SuperB, plus possible applications of crab-waist collisions for the LHC upgrade. Discussions during the workshop addressed the performance and limitations of the IR-upgrade optics performance, the optimization of new LHC triplet magnets, the US-LARP magnet strategy (response to Lucio Rossi’s “challenge”), heat deposition, earlyseparation dipoles, detector-integrated quadrupoles, strategy for crab cavities, beam–beam wire compensators, and crab-waist collisions. At IR’07 all auxiliary systems, e.g. wires and crab cavities, received a strong boost. Energy deposition was shown to add an important criterion to the optics requirements—in a first attempt a 2-cm thick stainless-steel liner was considered; more realistic configurations will need to be explored in the future. Improved upgrade designs presented at IR’07 promise higher and better luminosity than earlier scenarios. Some remaining uncertainties for Nb$_{3}$Sn magnets were identified, for example concerning field quality and temperature margin. Only two IR upgrade optics versions were retained from a larger number of earlier proposals, namely the so-called “low β-max” and “symmetric” optics. Conflicting time scales were evidenced: the accelerator input to the experiments is requested almost immediately, while the experiments require first LHC physics results to determine the boundary conditions for the accelerator upgrade. Finally, IR07 confirmed the three principal LHC high-luminosity upgrade paths: early separation, full crab crossing, and large Piwinski-angle scheme

IR ranking proposal and new beam parameter sets for the LHC upgrade: the view of HHH

We propose a ranking for the interaction-region (IR) optics based on the presentations and results from the first two days of the LUMI’06 workshop